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GeForce GT 640 DDR3 vs Radeon HD 4850 X2 1GB

Intro

The GeForce GT 640 DDR3 comes with a GPU clock speed of 900 MHz, and the 2048 MB of DDR3 memory is set to run at 1782 MHz through a 128-bit bus. It also is comprised of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

Compare that to the Radeon HD 4850 X2 1GB, which makes use of a 55 nm design. AMD has set the core frequency at 625 MHz. The GDDR3 memory runs at a speed of 993 MHz on this specific model. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3 65 Watts
Radeon HD 4850 X2 1GB 250 Watts
Difference: 185 Watts (285%)

Memory Bandwidth

Theoretically, the Radeon HD 4850 X2 1GB should perform a lot faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4850 X2 1GB 127104 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 70080 (123%)

Texel Rate

The Radeon HD 4850 X2 1GB should be much (more or less 74%) more effective at AF than the GeForce GT 640 DDR3. (explain)

Radeon HD 4850 X2 1GB 50000 Mtexels/sec
GeForce GT 640 DDR3 28800 Mtexels/sec
Difference: 21200 (74%)

Pixel Rate

The Radeon HD 4850 X2 1GB will be much (about 39%) faster with regards to AA than the GeForce GT 640 DDR3, and will be capable of handling higher screen resolutions better. (explain)

Radeon HD 4850 X2 1GB 20000 Mpixels/sec
GeForce GT 640 DDR3 14400 Mpixels/sec
Difference: 5600 (39%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

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GeForce GT 640 DDR3

Amazon.com

Check prices at:

Radeon HD 4850 X2 1GB

Amazon.com

Check prices at:

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

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Model GeForce GT 640 DDR3 Radeon HD 4850 X2 1GB
Manufacturer nVidia AMD
Year June 2012 Nov 7, 2008
Code Name GK107 R700
Memory 2048 MB 1024 MB (x2)
Core Speed 900 MHz 625 MHz (x2)
Memory Speed 3564 MHz 1986 MHz (x2)
Power (Max TDP) 65 watts 250 watts
Bandwidth 57024 MB/sec 127104 MB/sec
Texel Rate 28800 Mtexels/sec 50000 Mtexels/sec
Pixel Rate 14400 Mpixels/sec 20000 Mpixels/sec
Unified Shaders 384 800(160x5) (x2)
Texture Mapping Units 32 40 (x2)
Render Output Units 16 16 (x2)
Bus Type DDR3 GDDR3
Bus Width 128-bit 256-bit (x2)
Fab Process 28 nm 55 nm
Transistors 1300 million 956 million
Bus PCIe 3.0 x16 PCIe 2.0 x16 (PCIe bridge)
DirectX Version DirectX 11.0 DirectX 10.1
OpenGL Version OpenGL 4.2 OpenGL 3.0

Memory Bandwidth: Bandwidth is the max amount of information (counted in MB per second) that can be transferred past the external memory interface within a second. It's worked out by multiplying the interface width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This figure is worked out by multiplying the total texture units by the core speed of the chip. The higher the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.

Display Prices

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GeForce GT 640 DDR3

Amazon.com

Check prices at:

Radeon HD 4850 X2 1GB

Amazon.com

Check prices at:

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

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